New functionally dioecious bush tomato from northwestern Australia, Solanum ossicruentum, may utilize "trample burr" dispersal.

Alice Butler,Jason Cantley,Christopher Martine,Emma Frawley,Ingrid Jordon-Thaden

doi:10.3897/phytokeys.63.7743

Abstract

A new Australian species of functionally dioecious bush tomato of Solanum subgenus Leptostemonum is described. Solanum ossicruentum Martine & J.Cantley, sp. nov., is thought to be allied with members of the problematic “Dioicum Complex” lineage, but differs in its short silvery indumentum, long calyx lobes, larger stature, and an unusual fruit morphology that may represent “trample burr” seed dispersal. The species occurs in a range extending from the eastern Kimberley in Western Australia to far northwestern Northern Territory and has been recognized for decades as a variant of Solanum dioicum W.Fitzg. Specimens of this species were previously referred to by D.E. Symon and others as Solanum dioicum ‘Tanami.’ Ex situ crossing studies and SEM images of inaperturate pollen grains produced in morphologically hermaphrodite flowers indicate that this taxon is functionally dioecious. The scientific name was chosen with the help of 150 seventh grade life science students from Pennsylvania, USA.

Highlights

Dioecy in Solanum (Solanaceae) is one of the more fascinating phenomena in plant reproductive biology (Knapp et al 1998)
Recent observations of the taxon by CTM in Mirima National Park (WA), the Carr Boyd Ranges (WA), and Keep River National Park (NT) are combined here with inferences from plants grown in cultivation from wild-collected seed and herbarium sheets held at the Northern Territory Herbarium, Palmerston (DNA)
A small set (n=8) of ex situ hand pollinations conducted for this study showed that inaperturate pollen produced by functional females does not lead to fruit set when used to pollinate other females – suggesting that, like other dioecious solanums, reproduction in this species is dependent on intersexual outcrossing via biotic pollination

Summary

Introduction

Dioecy in Solanum (Solanaceae) is one of the more fascinating phenomena in plant reproductive biology (Knapp et al 1998) Species exhibiting this breeding system do so in a functional sense whereby male plants bear morphologically staminate flowers and female plants bear morphologically hermaphrodite flowers with anthers that (typically) produce inaperturate pollen. Symon (1981) identified three widespread and recognizably different forms of the broadly circumscribed S. dioicum, identifying ‘Tanami’ as an inland form occupying the “eastern margin” of the species range and noted its distinctiveness in being “closely and densely silvery-pubescent, compact, and extremely prickly.”. We describe this form as a new species of Solanum Symon (1981) identified three widespread and recognizably different forms of the broadly circumscribed S. dioicum, identifying ‘Tanami’ as an inland form occupying the “eastern margin” of the species range and noted its distinctiveness in being “closely and densely silvery-pubescent, compact, and extremely prickly.” Here we describe this form as a new species of Solanum

Methods

Discussion